Recently, in the field of automatic ticket checkers or electronic money systems, a non-contact IC card is in use. This non-contact IC card includes, within the bulk of the card, an IC (integrated circuit) chip, composed of various electronic circuits, adapted for performing various processing operations for data write/readout, and a loop coil antenna, composed of a conductor wound in a flat configuration. The non-contact IC card exploits the a.c. voltage, induced in a loop coil antenna provided to the non-contact IC card, under an a.c. magnetic field of, for example, 13.56 MHz, generated in the loop coil antenna provided to a reader/writer adapted to write or read out data for the non-contact IC card, on the basis of the principle of electromagnetic induction, as a power supply for actuating an IC chip. Moreover, the non-contact IC card has non-contact data communication with the reader/writer by changing the load impedance.
Thus, with the present non-contact IC card, in which the power as needed is supplied from the reader/writer, there is no necessity of providing an internal power supply, such that the data write/readout operation may be carried out with ease speedily, simply by momentarily holding the card over the reader/writer.
Meanwhile, in view of user-friendliness of the non-contact IC card, it is now being contemplated to have the above-described non-contact IC card mounted on e.g. a portable device, such as a cellular phone, so that the portable device itself may serve as the non-contact device for wireless near-distance transmission, without the necessity for a user to carry about the card, as disclosed in the Japanese laid-Open Patent publication 11-213111.
However, if, with the above-described data communication apparatus, the planar loop coil antenna 101, mounted on the non-contact IC card, is arranged in an enclosure 100 of a veritable thickness, such as the cellular phone schematically shown in FIG. 7, sensitivity offset occurs across one of the major surfaces of the enclosure 100, in which the loop coil antenna 101 is arranged, and the other major surface, thus deteriorating the user friendliness. That is, if the planar loop coil antenna 101 is arranged within the inside of the enclosure 100, having the veritable thickness, such a problem is raised in which the sensitivity of the loop coil antenna 101 is changed with the orientation or the sensitivity area becomes smaller in size.
Thus, for equalizing the sensitivity of the loop coil antenna 101 across both major surfaces of the loop coil antenna 101, the planar loop coil antenna 101 must be arranged centrally in the enclosure 100. However, if, with the portable device, such as the aforementioned cellular phone, this planar loop coil antenna is arranged centrally in the enclosure, there is imposed significant mounting constraint.
Moreover, if, with the above-described loop coil antenna 101, the number of turns of the conductor is increased, the opening area of the loop coil antenna is decreased, thus narrowing down the area of sensitivity of communication with the reader/writer.